The present application relates to a non-aqueous electrolyte battery and a method for producing a non-aqueous electrolyte battery. More particularly, the present application relates to a non-aqueous electrolyte battery having high strength and providing a satisfactory safety and a method for producing a non-aqueous electrolyte battery.
In recent years, various types of portable electronic devices, such as camera-integrated video tape recorders (VTRs), cell phones, and laptop computers, come on the market, and those having smaller size and weight are being developed. As the portable electronic devices are reduced in size and weight, demand for battery as a power source of them is rapidly increasing, and, for reducing the size and weight of the device, a battery for the device is required to be designed so that the battery is lightweight and thin, and efficiently uses the space in the device. As a battery that can meet such demands, a lithium-ion secondary battery having a large energy density and a large power density is the most preferable.
In a common lithium-ion secondary battery, for achieving high productivity, a structure is used such that a separator is disposed between generally a strip-shaped positive electrode and a strip-shaped negative electrode and they are stacked on one another and spirally wound together into a cylindrical or substantially elliptic shape to form a battery element and the battery element is sealed in a casing member material, together with an electrolytic solution or electrolyte. Alternatively, there can be used a structure of device in which a plurality of basic stacked units are stacked on one another wherein each basic stacked unit includes a flat-shaped positive electrode, a separator, and a flat-shaped negative electrode. When such a stacked structure is used, positive and negative electrode leads can be easily led from each basic stacked unit, thereby making it possible to reduce the internal current collection resistance while maintaining a simple structure and high productivity.
As described above, the battery element having a spirally wound structure or a stacked structure can be a substantially rectangular shape. Accordingly, as a casing member material covering the battery element, there can be employed a metal laminated film having a basic structure including a polymer film, a metallic foil, and a polymer film which are staked on one another into a laminated structure. A casing member material composed of a metal laminated film can considerably reduce the battery weight, as compared to a casing member material made of a metal, and therefore possibly realizes a battery advantageously used in applications that require a high-power and light-weight battery, such as hybrid cars and electric cars. Further, the use of a casing member material made of a metal needs the cost of processing of the casing member material, such as drawing or welding, but the use of a metal laminated film can reduce the cost of processing, thereby making it possible to reduce the cost of production.
The battery using a casing member material composed of a metal laminated film is produced as follows. A metal laminated film is first subjected to deep drawing to form a space for containing a battery element therein, and a battery element is placed in the space. Then, the opening of the space containing therein the battery element is covered with the metal laminated film, and then the metal laminated film around the space is heat-sealed, so that the battery element is sealed in the laminated film. When sealing the battery element in the metal laminated film, lead portions of the individual positive and negative electrodes are extended to the outside of the casing member through the heat-sealed portion of the laminated film, thereby forming external electrode terminals.
The non-aqueous electrolyte battery using a metal laminated film as a casing member material can be reduced in weight and thickness, and further can reduce the cost of production; however, this battery has a problem of poor battery strength.
For solving the problem, the patent documents 1 to 3 below, discloses a non-aqueous electrolyte battery having improved strength such that the non-aqueous electrolyte battery described above is contained in a resin molded case formed by molding a plastic.
[Patent document 1] Japanese Patent No. 3556875
[Patent document 2] Japanese Patent No. 3614767
[Patent document 3] Japanese Patent No. 3643792
The resin molded case includes, for example, separate upper and lower cases, and the upper case and lower case are fitted to each other and connected together to form a housing having a space for containing the non-aqueous electrolyte battery therein and a circuit board connected to the non-aqueous electrolyte battery.
Further, the Japanese Unexamined Patent Application Publication No. 2003-168410 (Patent document 4) discloses a battery having a construction advantageous not only in that the battery strength is improved, but also in that, when gas is generated from the non-aqueous electrolyte battery due to decomposition of the electrolyte or the like, the gas can be discharged from the non-aqueous electrolyte battery.
The battery described in the patent document 4 includes a non-aqueous electrolyte battery covered with a metal laminated film, which is contained in a case having a protrusion inside of the case, and, when gas is generated in the non-aqueous electrolyte battery, the non-aqueous electrolyte battery expands and comes into contact with the protrusion formed inside of the case, so that the protrusion penetrates the metal laminated film. The protrusion formed inside of the case has therein a through hole communicating the tip of the protrusion with the outside of the case. By virtue of the through hole, when the protrusion sticks in the non-aqueous electrolyte battery, the gas generated in the non-aqueous electrolyte battery can be discharged to outside from the case.
As another method for securing the battery strength, the use of a spacer made of a resin inside the metal laminated film has been proposed as described in the Unexamined Japanese Patent Application Publication No. 2005-285557 (Patent document 5).
In the patent document 5, a spacer is formed along the form of the side portion of the battery element having a flat form, and both the battery element and the spacer are covered with a metal laminated film. By virtue of this structure, the battery element can be prevented from deforming even when an external pressure is applied to the battery element, thereby improving the battery strength.
The spacer may be in a form such that the four sides are continued and the battery element is contained in a pore portion formed in the center of the spacer.